## Search found 59 matches

Sun Mar 17, 2019 4:44 pm
Forum: Second Order Reactions
Topic: Non-integer orders
Replies: 7
Views: 387

### Re: Non-integer orders

The only non-integer order which is mentioned in the book which occurs commonly would be the 1/2 order, but the rest should be ranging from 0-3 at most.
Sun Mar 17, 2019 4:43 pm
Forum: Second Order Reactions
Topic: Half Life
Replies: 7
Views: 855

### Re: Half Life

Half life equations are given in the equation sheet, but they will not tell you which half-life equation corresponds to which order of reaction. You can also derive them using the standard half life equation, solving for t when the concentrations are half of the initial.
Sun Mar 17, 2019 4:41 pm
Forum: Zero Order Reactions
Topic: Reaction Rate
Replies: 10
Views: 566

### Re: Reaction Rate

when given a table, you can use any reaction and the values to kind K, right? Yes, you should be able to use any of the values given to find k as long as they correspond to one another. For example, using random concentrations for an initial rate which was found using other concentrations would not...
Sun Mar 17, 2019 4:35 pm
Forum: Zero Order Reactions
Topic: Reaction Rate
Replies: 10
Views: 566

### Re: Reaction Rate

What is a reaction rate and how does it relate to the rate law? The reaction rate is the rate of which the reaction proceeds (in M/s) and is related to the rate law as the rate law is used to calculate the initial rates of the reaction. In a problem typically we would use the reaction rate to find ...
Sun Mar 17, 2019 4:34 pm
Forum: Zero Order Reactions
Topic: Reaction Rate
Replies: 10
Views: 566

### Re: Reaction Rate

Yes, the K value should be the same for all since you need to use the different concentrations and initial rates in order to find K in the first place.
Sun Mar 17, 2019 4:33 pm
Forum: Zero Order Reactions
Topic: Zero Order Reaction Example
Replies: 6
Views: 375

### Re: Zero Order Reaction Example

A zero order reaction is one where changing the concentration of your reactants does not change the initial rate of the reaction, meaning that your reaction rate is independant of that reactant. Zero order reaction K values will have M/s units.
Sun Mar 17, 2019 4:30 pm
Forum: Zero Order Reactions
Topic: Zero order reaction
Replies: 8
Views: 464

### Re: Zero order reaction

You can determine experimentally, when observing that the initial rates don't change when changing the concentration of the reactants, or by looking at your K units as your K would have to be in the units of M/s to offset the unitless reactant.
Sun Mar 17, 2019 4:03 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equlibrium and catalysts
Replies: 2
Views: 255

### Re: Equlibrium and catalysts

Catalysts lower the activation energy needed for a reaction to proceed, but should not innately change anything about the equilibrium. It would only serve to shift the reaction to the right as more products would be made.
Sun Mar 17, 2019 3:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K and Kc
Replies: 6
Views: 461

### Re: K and Kc

K and Kc can mean similar things depending on the context of the problem, but Kp would mean partial pressures while Kc would mean concentration.
Sun Mar 17, 2019 3:47 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka Kb = Kw
Replies: 5
Views: 484

### Re: Ka Kb = Kw

Kw is typically used to find Ka or Kb when given the other. The relation can be used in any number of ways depending on the problem and what you need to find.
Sun Mar 17, 2019 3:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka vs. Kb
Replies: 12
Views: 718

### Re: Ka vs. Kb

Ka is the ionisation constant, used when dealing with acids and excess protons in a solution. Kb is typically used with bases, and finding the pOH of a solution. Kc is just the relation of Ka and Kb which is Ka X Kb = 10^-14
Sun Mar 17, 2019 3:33 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: atm to torr
Replies: 3
Views: 350

### Re: atm to torr

1 ATM = 760 torr and it is always on the equation sheet! Just remember to use the correct constants after converting from atm to torr!
Sun Mar 17, 2019 3:28 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Deriving Enthalpy Equations
Replies: 3
Views: 346

### Re: Deriving Enthalpy Equations

For any derivations which I've had to do I always start by finding common factors/variables and playing around with them with substitution until I get the equation whic I need. Always look at which variables need to cancel and which ones you would need to keep, it is a crucial factor in derivations.
Sun Mar 17, 2019 3:25 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: [tex]\Delta U = \Delta H[/tex]
Replies: 2
Views: 426

### Re: [tex]\Delta U = \Delta H[/tex]

So delta U = delta H is only considered a very specific case of the original equation, which is delta U = q + w = q - P delta V. You can only use delta U = delta H when q = delta H and you are under constant pressure, otherwise you cannot use the other equation.
Sun Mar 17, 2019 3:22 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: delta H of reaction
Replies: 2
Views: 363

### Re: delta H of reaction

Enthalpy is a property which varies with the moles of reactants/products present, and oftentimes the units would be KJ/mole or would ask you to find it permole, so it makes sense to make stoichiometrically correct calculations when finding the enthalpy of the reaction.
Sun Mar 17, 2019 3:19 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Cp vs Cv
Replies: 6
Views: 1070

### Re: Cp vs Cv

Cp represents constant pressure while Cv represents constant volume, our problems will tell us whether or not we would be dealing with constant pressure or volume as one with two changing conditions would be extremely difficult, and would have to use another approach entirely.
Sun Mar 17, 2019 3:17 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Midterm Question 6
Replies: 6
Views: 540

### Re: Midterm Question 6

I think for this question on the midterm it was far easier to approach it by finding the net moles of gas produced than it was to calculate each bond enthalpy as you have delta U = delta H (which is found by multiplying the delta H given by 4 moles) - nRT where your n is just the net change in moles...
Sun Mar 17, 2019 3:13 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: q and delta H
Replies: 6
Views: 519

### Re: q and delta H

So Delta U = q + w = q - PdeltaV, meaning that under constant pressure U = q = delta H. This is where most of the interchangeability comes from as systems with constant pressure appear often in our problems.
Sun Mar 17, 2019 3:11 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: When is delta U = 0?
Replies: 4
Views: 436

### Re: When is delta U = 0?

Looking at the equation Delta U = q + w, delta U is only 0 when q = -w which means heat put into the system is equal to the heat out of the system, in other words the system is isolated with no net change in internal energy.
Sun Mar 17, 2019 3:08 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Drawing cells
Replies: 3
Views: 327

### Re: Drawing cells

A general cell diagram would be something like this for a Galvanic cell:

Conducting Solid | Anode || Cathode | Conducting Solid

Different states of matter are separated by | while different species of the same state are separated by commas
Sun Mar 17, 2019 3:06 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Test #2: Question #4, Parts A and B
Replies: 2
Views: 302

### Re: Test #2: Question #4, Parts A and B

The balanced overall cell reaction that I got was 2N02 + 2H20 + Zn2+ --> Zn (S) + NO3- + 4H+, and I also got the cell diagram wrong. However from what I can ascertain you needed to flip No3 and Zn, and include a solid for the NO3 side.
Sun Mar 17, 2019 3:01 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: E cell
Replies: 3
Views: 343

### Re: E cell

It's not usually negative in the way that time can't be negative in a physics problem, but for the sake of some calculations we can set it to be negative. When flipping the equation for a half reaction your E can be negative at times, which may contribute to this as well.
Sun Mar 17, 2019 2:58 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram and Ecell [ENDORSED]
Replies: 10
Views: 39570

### Re: Cell Diagram and Ecell[ENDORSED]

For a Galvanic Cell it should be Anode || Cathode, where there are single lines (|) separating different states of matter, and commas separating different agents with the same state of matter. i.e (aq), (aq), || (aq)| (s)
Sun Mar 17, 2019 2:56 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Reducing Power
Replies: 3
Views: 357

### Re: Reducing Power

It is due to the fact that a stronger reduction power indicates higher electronegativity, which makes for a stronger oxidising agent. Stronger reduction power also corresponds with a higher E value, which also increases oxidising power.
Tue Feb 12, 2019 10:21 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Equations
Replies: 5
Views: 481

### Equations

Which equations would be good to memorise for the midterm?
Tue Feb 12, 2019 10:20 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Midterm #1 14B
Replies: 17
Views: 1028

### Re: Midterm #1 14B

I don't see any other worksheets posted :(
Tue Feb 12, 2019 10:19 pm
Forum: Administrative Questions and Class Announcements
Topic: Lyndon's HOTDOG MIDTERM REVIEW SESSION!! FINALLY!
Replies: 49
Views: 3917

### Re: Lyndon's HOTDOG MIDTERM REVIEW SESSION!! FINALLY!

Are there answers to these problems?
Fri Jan 18, 2019 11:03 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka vs. Kb
Replies: 12
Views: 718

### Re: Ka vs. Kb

Ka and Kb are just used for acid/base dissociation, and Kc is just the equilibrium concentration.
Fri Jan 18, 2019 11:00 am
Forum: Ideal Gases
Topic: Chemistry Community Posting
Replies: 7
Views: 265

### Chemistry Community Posting

Should we finish our three posts before our discussion date or before/on Friday?
Fri Jan 18, 2019 10:59 am
Forum: Ideal Gases
Topic: Homework Week 2
Replies: 10
Views: 429

### Re: Homework Week 2

Homework will now be due in discussion!
Sat Dec 08, 2018 12:06 am
Forum: Ionic & Covalent Bonds
Topic: Test bank?
Replies: 9
Views: 1090

### Re: Test bank?

Anyone have any past final exam questions from Lavelle from the test bank?
Sat Dec 08, 2018 12:00 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: strong vs weak acids
Replies: 5
Views: 240

### Re: strong vs weak acids

Electronegativity is also a factor to consider!
Fri Dec 07, 2018 11:59 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Oxygen atoms in acid structures?
Replies: 3
Views: 394

### Re: Oxygen atoms in acid structures?

I'm guessing it's because this would make the molecule larger while also making it more electronegative, which makes it a stronger acid, but I'm not 100% sure.
Fri Dec 07, 2018 11:56 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Factors for Acid Stength [ENDORSED]
Replies: 3
Views: 301

### Re: Factors for Acid Stength[ENDORSED]

The more electronegative the atom is the stronger the acid due to the strong ionic nature of their electron-sharing nature!
Fri Nov 30, 2018 1:57 pm
Forum: Administrative Questions and Class Announcements
Topic: How to find my posts
Replies: 74
Views: 48813

### Re: How to find my posts

I believer you can have email notifications, but I'm not sure how practical that would be.
Fri Nov 30, 2018 10:59 am
Forum: Air Pollution & Acid Rain
Topic: Acid Rain on the Final
Replies: 4
Views: 441

### Acid Rain on the Final

Will we have to memorise the exact chemical reaction equation for acid rain?
Fri Nov 30, 2018 10:39 am
Forum: Air Pollution & Acid Rain
Topic: Acid Rain
Replies: 15
Views: 1478

### Re: Acid Rain

The water molecules in rain react with pollutants in the air and becomes acidic in nature
Fri Nov 30, 2018 10:38 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH formula
Replies: 5
Views: 453

### Re: pH formula

They might give us a new equation sheet but I'm pretty sure you're just supposed to memorise it.
Fri Nov 30, 2018 10:37 am
Forum: Formal Charge and Oxidation Numbers
Topic: TEST 3
Replies: 4
Views: 485

### Re: TEST 3

I would not think so, though it's a relatively simple formula so they might expect you to memorise it.
Fri Nov 30, 2018 10:36 am
Forum: Sigma & Pi Bonds
Topic: Sigma and Pi bonds
Replies: 5
Views: 219

### Re: Sigma and Pi bonds

Most likely nothing computational as we don't know enough to do that, I would assume just labeling would work
Fri Nov 30, 2018 10:35 am
Forum: Calculating the pH of Salt Solutions
Topic: Ka Constant
Replies: 4
Views: 395

### Ka Constant

Do we need to know how to calculate the Ka equilibrium of acid/base reactions?
Sat Nov 17, 2018 1:56 am
Forum: Sigma & Pi Bonds
Topic: Sigma v. Pi
Replies: 6
Views: 415

### Re: Sigma v. Pi

Sigma bonds result from overlapping end-end atomic orbitals while pi bonds are overlapping side to side in a perpendicular plane.
Sat Nov 17, 2018 1:55 am
Forum: Sigma & Pi Bonds
Topic: Double Bonds and Triple Bonds
Replies: 2
Views: 199

### Re: Double Bonds and Triple Bonds

Sat Nov 17, 2018 1:53 am
Forum: Hybridization
Topic: Test 3
Replies: 5
Views: 333

### Re: Test 3

His outline would give all necessary information, and he would probably email us as well soon!
Sun Nov 04, 2018 9:58 pm
Forum: Electronegativity
Topic: Periodic Trends
Replies: 10
Views: 614

### Re: Periodic Trends

For Atomic Radius it increases as it goes down due to the added number of shells to house the electrons
Sun Nov 04, 2018 9:57 pm
Forum: Electronegativity
Topic: MIDTERM
Replies: 5
Views: 228

### Re: MIDTERM

Will we be given the electronegativity difference numbers for non-obvious cases of covalent or ionic bonding?
Sun Nov 04, 2018 9:56 pm
Forum: Ionic & Covalent Bonds
Topic: Test bank?
Replies: 9
Views: 1090

### Re: Test bank?

The Bruin Online Testbank has previous chem 14A exams too but not from Lavelle
Thu Oct 25, 2018 11:18 pm
Forum: Photoelectric Effect
Topic: Conditions that allow electron to be ejected from metal surface
Replies: 12
Views: 844

### Re: Conditions that allow electron to be ejected from metal surface

Will the work function of the metal be given when doing problems?
Thu Oct 25, 2018 11:15 pm
Forum: Properties of Light
Topic: Test 2
Replies: 7
Views: 363

### Re: Test 2

Which equations do we have to memorise vs which ones are on the equation sheet?
Thu Oct 25, 2018 11:14 pm
Forum: Einstein Equation
Topic: Units
Replies: 17
Views: 936

### Re: Units

It should follow e=mc^2 for photons, which is kgm^2/s^2
Thu Oct 18, 2018 7:57 pm
Forum: Properties of Electrons
Topic: Diffraction patterns
Replies: 9
Views: 474

### Re: Diffraction patterns

Constructive interference simply means that an addition of the two waves results in a larger amplitude, while destructive interference is the opposite. The two are not mutually exclusive and can be in conjunction with one another.
Thu Oct 18, 2018 7:55 pm
Forum: Properties of Electrons
Topic: Energy v. Kinetic Energy
Replies: 3
Views: 147

### Re: Energy v. Kinetic Energy

Electrons have different properties than photons, and while it is near massless, it is often not considered as such when solving for kinetic energy which is why the same kinetic energy equations which work for photons do not work for electrons.
Thu Oct 18, 2018 7:53 pm
Forum: Properties of Light
Topic: Wavelength and frequency proportions [ENDORSED]
Replies: 5
Views: 336

### Re: Wavelength and frequency proportions[ENDORSED]

The two have an inversely proportional relationship, this property is just derived from the formula!
Fri Oct 12, 2018 12:12 am
Forum: Administrative Questions and Class Announcements
Topic: Number of questions on test one [ENDORSED]
Replies: 39
Views: 18592

### Re: Number of questions on test one[ENDORSED]

Does anyone know if there will be a periodic table provided for us?
Fri Oct 12, 2018 12:10 am
Forum: SI Units, Unit Conversions
Topic: formula units [ENDORSED]
Replies: 69
Views: 24880

### Re:[ENDORSED]

Simran Athwal-Dis 3A wrote:Hi, I had a quick question. How do we check how many times we posted on Chemistry Community? Do we go on our profile?

I think theres an option in profile which shows your posts!
Fri Oct 12, 2018 12:08 am
Forum: Administrative Questions and Class Announcements
Topic: Number of questions on test one [ENDORSED]
Replies: 39
Views: 18592

### Re: Number of questions on test one[ENDORSED]

Diana Chavez 1K wrote:If we do not understand what a question on the test asks is it allowed to ask for clarity from our TA's?

I think in general during testing they're not really allowed to answer these types of questions unless it's a glaring wording error.
Mon Oct 01, 2018 1:57 pm
Forum: Significant Figures
Topic: Significant Figures [ENDORSED]
Replies: 6
Views: 233

### Re: Significant Figures[ENDORSED]

Significant figures allows us to measure the precision of our measurement instruments!
Mon Oct 01, 2018 1:54 pm
Forum: SI Units, Unit Conversions
Topic: Week 1 Homework Assignment [ENDORSED]
Replies: 16
Views: 729

### Re: Week 1 Homework Assignment[ENDORSED]

Yep! You do any seven problems from the assigned problems and turn it in.
Mon Oct 01, 2018 2:58 am
Forum: SI Units, Unit Conversions
Topic: Homework Grading Clarification [ENDORSED]
Replies: 8
Views: 496

### Homework Grading Clarification[ENDORSED]

So for the homework we turn in, do we pick seven problems from the list on the syllabus or should we turn in our answers to all of the problems but the TAs would only grade seven of them?

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